The invention provides isolated nucleic acid and amino acid sequences of HsKif21b, methods of detecting HsKif21b and screening for HsKif21b modulators using biologically active HsKif21b, and kits for screening for HsKif21b modulators.
The kinesin superfamily is an extended family of related microtubule motor proteins. It can be classified into at least 8 subfamilies based on primary amino acid sequence, domain structure, velocity of movement, and cellular function. This family is exemplified by xe2x80x9ctruexe2x80x9d kinesin, which was first isolated from the axoplasm of squid, where it is believed to play a role in anterograde axonal transport of vesicles and organelles (see, e.g., Goldstein, Annu. Rev. Genet. 27:319-351 (1993)). Kinesin uses ATP to generate force and directional movement associated with microtubules.
KIF (KInesin Family) proteins are microtubule-dependent molecular motors that play important roles in intracellular transport and cell division. More specifically, several of these kinesins have been found associated with the arms of mitotic chromosomes. These kinesins are thought to provide a force, sometimes referred to as the polar ejection force, that is directed away from each spindle pole and is thought to contribute to movement of mitotic chromosomes toward the mitotic spindle midzone during prometaphase of mitosis. These kinesins are sometimes collectively referred to as chromokinesins. Within this functional group of kinesins resides a group of kinesins from several organisms that share significant sequence homology, i.e., the chromokinesin subfamily.
These include human Kif4 (HsKif4), murine Kif4 (MmKif4), and Xenopus laevis XKlp1, which are all closely related and are probably functional orthologs. Drosophila nod, and Drosophila Klp3A and C. elegans ChromoK-A and -B are more distantly related, but also appear to function during mitosis.
Mouse Kif21b has been identified and appears to be a plus-end directed motor, localized to neuronal dendrites. See, Marszalek et al. (1999) J. Cell Biol. 145:469.
The discovery of a new kinesin motor protein, and more particularly, one in the chromokinesin subfamily, and the polynucleotides encoding it satisfies a need in the art by providing new compositions which are useful in the diagnosis, prevention, and treatment of cancer, neurological disorders, and disorders of vesicular transport.
The present invention is based on the discovery of a new human kinesin motor protein, HsKif21b, the polynucleotide encoding HsKif21b, and the use of these compositions for the diagnosis, treatment, or prevention of cancer, neurological disorders, and disorders of vesicular transport.
In one aspect, the invention provides an isolated nucleic acid sequence encoding a kinesin superfamily motor protein, wherein the motor protein has the following properties: (i) the protein""s activity includes microtubule stimulated ATPase activity; and (ii) the protein has a sequence that has greater than 70% amino acid sequence identity to SEQ ID NO:2 or SEQ ID NO:4 as measured using a sequence comparison algorithm. In one embodiment, the protein further specifically binds to polyclonal antibodies raised against SEQ ID NO:2 or SEQ ID NO:4.
In one embodiment, the nucleic acid encodes HsKif21b or a fragment thereof. In another embodiment, the nucleic acid encodes SEQ ID NO:2 or SEQ ID NO:4. In another embodiment, the nucleic acid has a nucleotide sequence of SEQ ID NO:1 or SEQ ID NO:3.
In one aspect, the nucleic acid comprises a sequence which encodes an amino acid sequence which has greater than 70% sequence identity with SEQ ID NO:2 or SEQ ID NO:4, preferably greater than 80%, more preferably greater than 90%, more preferably greater than 95% or, in another embodiment, has 98 to 100% sequence identity with SEQ ID NO:2 or SEQ ID NO:4.
In one embodiment, the nucleic acid comprises a sequence which has greater than 55 or 60% sequence identity with SEQ ID NO:1 or SEQ ID NO:3, preferably greater than 70%, more preferably greater than 80%, more preferably greater than 90 or 95% or, in another embodiment, has 98 to 100% sequence identity with SEQ ID NO:1 or SEQ ID NO:3. In another embodiment provided herein, the nucleic acid hybridizes under stringent conditions to a nucleic acid having a sequence or complementary sequence of SEQ ID NO:1 or SEQ ID NO:3.
In another aspect, the invention provides an expression vector comprising a nucleic acid encoding a kinesin superfamily motor protein, wherein the motor protein has the following properties: (i) the protein""s activity includes microtubule stimulated ATPase activity; and (ii) the protein has a sequence that has greater than 70% amino acid sequence identity to SEQ ID NO:2 or SEQ ID NO:4 as measured using a sequence comparison algorithm. The invention further provides a host cell transfected with the vector.
In another aspect, the invention provides an isolated kinesin superfamily motor protein, wherein the protein has one or more of the properties described above. In one embodiment, the protein specifically binds to polyclonal antibodies generated against a motor domain, tail domain or other fragment of HsKif21b. In another embodiment, the protein comprises an amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4.
In one aspect, the protein provided herein comprises an amino acid sequence which has greater than 70% sequence identity with SEQ ID NO:2 or SEQ ID NO:4, preferably greater than 80%, more preferably greater than 90%, more preferably greater than 95% or, in another embodiment, has 98 to 100% sequence identity with SEQ ID NO:2 or SEQ ID NO:4.
The invention features a substantially purified polypeptide comprising the amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4 or a fragment thereof and more particularly, the motor domain of the amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4 or a fragment thereof.
In one embodiment, the present invention provides a method of identifying a candidate agent as a modulator of the activity of a target protein. The method comprises adding a candidate agent to a mixture comprising a target protein which directly or indirectly produces ADP or phosphate, under conditions that normally allow the production of ADP or phosphate. The method further comprises subjecting the mixture to a reaction that uses said ADP or phosphate as a substrate under conditions that normally allow the ADP or phosphate to be utilized and determining the level of activity of the reaction as a measure of the concentration of ADP or phosphate. A change in the level between the presence and absence of the candidate agent indicates a modulator of the target protein.
The phrase xe2x80x9cuse ADP or phosphatexe2x80x9d means that the ADP or phosphate are directly acted upon by detection reagents. In one case, the ADP, for example, can be hydrolyzed or can be phosphorylated. As another example, the phosphate can be added to another compound. As used herein, in each of these cases, ADP or phosphate is acting as a substrate.
Preferably, the target protein either directly or indirectly produces ADP or phosphate and comprises a motor domain. More preferably, the target protein comprises a kinesin superfamily motor protein as described above and most preferably, the target protein comprises HsKif21b or a fragment thereof.
Also provided are modulators of the target protein including agents for the treatment of cellular proliferation, including cancer, hyperplasias, restenosis, cardiac hypertrophy, immune disorders and inflammation. The agents and compositions provided herein can be used in variety of applications which include the formulation of sprays, powders, and other compositions. Also provided herein are methods of treating cellular proliferation disorders such as cancer, hyperplasias, restenosis, cardiac hypertrophy, immune disorders and inflammation, for treating disorders associated with HsKif21b activity, and for inhibiting HsKif21b.